‘04 Subaru Forester stalled when I came to a full stop?

Hmmm....I'd start with draining the ATF and looking at it. If less than 3.5qts drained then you were too low. Refill w/ 3.5qts ATF and a bottle of seal conditioner in hopes deal expansion will cure the leak. If the ATF was really black repeat the drain/refill after a week, as you only get 40% of the ATF out with each drain. BUT, do NOT BACK-FLUSH the 4EAT at a convenient wrench's shop for $100 and in so risk clogging all the sensitive valves with crap. If you can't get normal trans operation after two ATF refreshes look elsewhere for the culprit. If not found you need a new-used transmission. Good luck.

Thank you TheSubaruGuruBoston. I refilled the transmission because it was BONE DRY. We’re going to see how it performs now.

Yikes! Ok. Being "bone dry" on the stick can mean anything from empty to still having about 4qts in the 4EAT. Regardless, you'll experience the symptoms because of insufficient pressure and probably cavitation too. I suspect you've drained whatever was in there (if anything), then filled as appropriate to the stick proper level (when warm, at idle). I'd then drive a bit to see if you've suffered internal damage (besides ego issues!). If all ok I'd look at the "new" fluid after a few drives. If dark brown or gray DRAIN IT AGAIN, and refill with 4qts fresh ATF and a bottle of seal conditioner (brand doesn't matter). See if leak stops within a week or two, noting any losses on the stick. If it's actually dripping out you need to have the trans pan cover resealed (Fujibond or similar). But don't bother with that yet, because if you've damaged the trans you'll be throwing it away and chasing a "new" used one. Do NOT to let anyone take your money to rebuild it...doesn't ever end well. Good luck. Ern TSG/B